Various methods have been suggested as a method of refining grains of a titanium alloy. Recently, a method of refining grains of a titanium alloy by using equal channel angular pressing (ECAP) was disclosed in Korean Patent Application Laid-Open Publication No. 10-2006-0087077 (Aug. 2, 2006), a prior application by the present applicant.
The content of this patent relates to a method of preparing a nanocrystalline titanium alloy having excellent properties by performing ECAP on a titanium alloy material and a nanocrystalline titanium alloy prepared thereby. In the method of preparing a nanocrystalline titanium alloy of the foregoing patent, the titanium alloy material is processed by being introduced into a bent channel of an ECAP apparatus. When this is described in more detail, ECAP under a constant temperature condition is performed at least twice on the titanium alloy material. Herein, when the ECAP is performed after the second ECAP, the titanium alloy material is introduced in a state of being rotated with respect to the previous ECAP based on a central axis passing the center of the channel inlet and processed.
However, the foregoing method is a method of refining grains of a titanium alloy by applying high strain ranging from 4 to 8. A technique for refining grains at low strain is required for expanding applications of a nanocrystalline titanium alloy.